Biomedical subjects

Werner Müller

Publications and source records attributed to Werner Müller.

31 records · Page 2Linked to original sources

PubMed2004

Keratin 14 Cre transgenic mice authenticate keratin 14 as an oocyte-expressed protein.

Three mouse lines expressing Cre recombinase under the control of the human K14 promoter induced specific deletion of loxP flanked target sequences in the epidermis, in tongue, and thymic epithelium of the offspring where the Cre allele was inherited from the father. Where the mother carried the Cre allele, loxP flanked sequences were completely deleted in all tissues of the offspring, even in littermates that did not inherit the Cre allele. This maternally inherited phenotype indicates that the human K14 promoter is transcriptionally active in murine oocytes and that the enzyme remains active until after fertilization, even when the Cre allele becomes transmitted to the polar bodies during meiosis. Detection of K14 mRNA by RT-PCR in murine ovaries and immunohistochemical identification of the K14 protein in oocytes demonstrates that the human K14 promoter behaves like its murine homolog, thus identifying K14 as an authentic oocytic protein.

Aging↗

PubMed2004

The European dimension for the mouse genome mutagenesis program.

The European Mouse Mutagenesis Consortium is the European initiative contributing to the international effort on functional annotation of the mouse genome. Its objectives are to establish and integrate mutagenesis platforms, gene expression resources, phenotyping units, storage and distribution centers and bioinformatics resources. The combined efforts will accelerate our understanding of gene function and of human health and disease.

Animals↗

PubMed2003

CD4+ T cell-associated pathophysiology critically depends on CD18 gene dose effects in a murine model of psoriasis.

In a CD18 hypomorphic polygenic PL/J mouse model, the severe reduction of CD18 (beta(2) integrin) to 2-16% of wild-type levels leads to the development of a psoriasiform skin disease. In this study, we analyzed the influence of reduced CD18 gene expression on T cell function, and its contribution to the pathogenesis of this disease. Both CD4(+) and CD8(+) T cells were significantly increased in the skin of affected CD18 hypomorphic mice. But only depletion of CD4(+) T cells, and not the removal of CD8(+) T cells, resulted in a complete clearance of the psoriasiform dermatitis. This indicates a central role of CD4(+) T cells in the pathogenesis of this disorder, further supported by the detection of several Th1-like cytokines released predominantly by CD4(+) T cells. In contrast to the CD18 hypomorphic mice, CD18 null mutants of the same strain did not develop the psoriasiform dermatitis. This is in part due to a lack of T cell emigration from dermal blood vessels, as experimental allergic contact dermatitis could be induced in CD18 hypomorphic and wild-type mice, but not in CD18 null mutants. Hence, 2-16% of CD18 gene expression is obviously sufficient for T cell emigration driving the inflammatory phenotype in CD18 hypomorphic mice. Our data suggest that the pathogenic involvement of CD4(+) T cells depends on a gene dose effect with a reduced expression of the CD18 protein in PL/J mice. This murine inflammatory skin model may also have relevance for human polygenic inflammatory diseases.

Animals↗

PubMed2003

Thymic stromal-derived lymphopoietin distinguishes fetal from adult B cell development.

Deletions of interleukin 7 (IL-7) or its receptor components permit fetal but not adult B cell development in mice. Mice deficient in IL-7 receptor alpha (IL-7R alpha) had 1% the number of B cells of controls and 10% that of mice deficient in the common gamma chain. As IL-7R alpha is also a receptor for thymic stromal-derived lymphopoietin (TSLP), we assayed the ability of TSLP to support proliferation of fetal or adult precursor B cells. Only fetal-derived pro-B cells were able to respond to TSLP, although pre-B cells from both origins were TSLP-responsive. Fetal but not adult precursors generated a measurable B cell compartment in the absence of IL-7. The residual B cells found in IL-7R alpha-deficient mice required fetal liver kinase 2 (Flk-2) for their development. Thus, IL-7R alpha- and Flk-2-mediated signals account for the generation of almost all mouse B lymphocytes.

Animals↗

PubMed2003

IL-15 is an essential mediator of peripheral NK-cell homeostasis.

Several distinct classes of surface receptors can, on ligand binding, transmit signals that modulate the survival, proliferation, and apoptosis of peripheral B, T, and natural killer (NK) cells. At the population level, dynamic changes in lymphocyte cell numbers are strictly regulated to maintain a steady state, a process referred to as homeostasis. Although several studies have investigated the signals that regulate B- and T-cell homeostasis, little is known about the mechanisms that control the survival and proliferation of peripheral NK cells. Using an adoptive transfer system, we have investigated the role of gammac-dependent cytokines, in particular interleukin 7 (IL-7) and IL-15, and major histocompatibility complex (MHC) class I molecules in peripheral NK-cell homeostasis. We observed that IL-15 plays a dominant role in the survival of peripheral NK cells, via maintenance of the antiapoptotic factor Bcl-2. IL-15 availability, however, also plays an important role because endogenous NK cells in the recipient mice influence the behavior of adoptively transferred NK cells. Finally, although NK cells bear functional inhibitory Ly49 receptors for MHC class I molecules, the presence or absence of specific ligands on host cells did not influence the survival or homeostatic expansion of donor NK cells.

Adoptive Transfer↗

PubMed2003

Mice with neonatally induced inactivation of the vascular cell adhesion molecule-1 fail to control the parasite in Toxoplasma encephalitis.

Under various inflammatory conditions, cell adhesion molecules are up-regulated in the central nervous system (CNS) and may contribute to the recruitment of leukocytes to the brain. In the present study, the functional role of vascular cell adhesion molecule (VCAM)-1 in Toxoplasma encephalitis (TE) was addressed using VCAM(flox/flox MxCre) mice. Neonatal inactivation of the VCAM-1 gene resulted in a lack of induction of VCAM-1 on cerebral blood vessel endothelial cells, whereas the constitutive expression of VCAM-1 on choroid plexus epithelial cells and the ependyma was unaffected; in these animals, resistance to T. gondii was abolished, and VCAM(flox/flox MxCre) mice died of chronic TE caused by a failure to control parasites in the CNS. Although leukocyte recruitment to the CNS was unimpaired, the B cell response was significantly reduced as evidenced by reduced serum levels of anti-T. gondii-specific IgM and IgG antibodies. Furthermore, the frequency and activation state of intracerebral T. gondii-specific T cells were decreased, and microglial activation was markedly reduced. Taken together, these data demonstrate the crucial requirement of VCAM-1-mediated immune reactions for the control of an intracerebral infectious pathogen, whereas other cell adhesion molecules can efficiently compensate for VCAM-1-mediated homing across cerebral blood vessels.

Animals↗

PubMed2003

Lack of gp130 expression in hepatocytes promotes liver injury.

BACKGROUND & AIMS: Interleukin 6 (IL-6) contributes via its signal transducer gp130 to the acute phase response (APR) in hepatocytes. Recent studies indicated that IL-6 is involved in the regulation of different pathophysiologic conditions of the liver. To define the IL-6-dependent intracellular pathways more specifically, we generated a hepatocyte-specific gp130 knockout mouse. METHODS: Hepatocyte-specific gp130-deficient mice were generated using the Cre-loxP system. Expression of the Cre recombinase was under the control of a hepatocyte-specific control element. Adult mice were challenged with IL-6, oncostatin M (OSM), and LPS. RESULTS: Cre expression started at day 10.5 postconception, and a complete deletion of gp130 in hepatocytes was found at day 14 during liver development. The adult liver of these mice showed no abnormalities; however, after IL-6 and OSM stimulation, gp130-dependent pathways (STAT3, APR gene expression) were completely blocked in the liver of these animals. Additionally, challenging hepatocyte-specific gp130 knockout animals with lipopolysaccharides (LPS) lead to an onset of acute liver injury with an increase of hepatocyte apoptosis associated with elevated tumor necrosis factor alpha (TNF-alpha) serum levels and reduced nuclear factor kappaB (NF-kappaB) activation in hepatocytes. CONCLUSIONS: Our findings demonstrate that gp130 is of minor relevance for embryonal development of hepatocytes. However, the molecule has an essential role in controlling acute phase gene expression and provides hepatocellular protection after LPS challenge.

Animals↗

PubMed2003

What to do in marine biotechnology?

During the symposium "Marine Biotechnology: Basics and Applications", held 25 February-1 March, 2003 in Matalascañas, Spain, a special brainstorm session was organized. Two questions were addressed: 1, "What is the most desirable development in marine biotechnology"?; 2, "What is the most spectacular development in this field in your 'wildest' dreams"? The outcome of this session is reported in this paper. From the more than 250 ideas generated, concern for the environment and human health emerged as the most significant issues.

Biotechnology↗

PubMed2003

Interleukin 6/gp130-dependent pathways are protective during chronic liver diseases.

The contribution of the acute phase inducer interleukin 6 (IL-6) in the pathogenesis of liver diseases is yet unclear. Our analysis showed enhanced expression of IL-6 in livers derived from patients with acute and chronic liver diseases. Additionally, IL-6 plasma levels were significantly increased in patients with chronic liver diseases and showed an inverse correlation with biochemical markers of liver function and a positive correlation with inflammatory markers, signs of portal hypertension, and the degree of liver fibrosis. To prove the relevance of these clinical findings, we applied the tetrachlorcarbonide (CCl(4)) model to conditional knockout animals (Cre/loxP system) for gp130, the common signal transducer of IL-6 family cytokines. Cre recombinases were expressed through a hepatocyte (AlfpCre) and a ubiquitous (MxCre) control element. Gp130 deleted mice had a totally abolished STAT3 activation and acute phase response induction, but gp130 deletion had no effect on the degree of acute liver injury and subsequent hepatocyte proliferation. In contrast, during chronic liver injury induced by biweekly application of CCl(4), deletion of the gp130 receptor in nonparenchymal liver cells and not hepatocytes resulted in fibrosis progression. In conclusion, our experiments indicate an involvement of IL-6 in the pathogenesis of liver diseases and suggest a protective role of IL-6/gp130-dependent pathways in nonparenchymal liver cells during fibrosis progression in chronic liver diseases. (Hepatology 2003;38:218-229).

Acute Disease↗

PubMed2002

Interleukin-6/glycoprotein 130-dependent pathways are protective during liver regeneration.

After tissue loss the liver has the unique capacity to restore its mass by hepatocyte proliferation. Interleukin-6 (IL6)-deficient mice show a lack in DNA synthesis after partial hepatectomy (PH). To define better the role of IL6 and its family members for liver regeneration after PH, we used conditional knockout mice for glycoprotein 130 (gp130), the common signal transducer of all IL6 family members. We show that gp130-dependent pathways control Stat3 activation after PH. By using gene array analysis, we demonstrate that c-jun, NF-kappa B, c-myc, and tumor necrosis factor receptor expression is gp130-dependent. However, in gp130-deleted mice only minor effects on cell cycle and on the maximum of DNA synthesis after PH were found compared with controls. As in conditional gp130 animals, the acute phase response was completely abolished, we considered that other means are essential to define the role of gp130-dependent pathways for liver regeneration. LPS stimulation in gp130-deleted and also IL6 -/- animals after PH leads to a significant reduction in survival and DNA synthesis, which was associated with decreased Bcl-xL expression and higher apoptosis in the liver. These results indicate that the phenotype concerning the reduction in DNA synthesis might be linked to the degree of infection after PH. Thus our results suggest that the role of gp130-dependent signaling is not a direct influence on cell cycle progression after partial hepatectomy but is to activate protective pathways important to enable hepatocyte proliferation.

Animals↗

PubMed2002

Monoclonal antibody against beta7 integrins, but not beta7 deficiency, attenuates intestinal allograft rejection in mice.

BACKGROUND: beta7 integrins mediate homing and retention of lymphocytes to the normal and inflamed small bowel in a tissue-selective fashion. In the present study, we investigated the expression of beta7 integrins after small bowel transplantation (SBT) and tested the effects of blocking beta7-mediated pathways by using monoclonal antibody (mAb) or knockout mice. METHODS: Heterotopic SBT from BALB/c to C57BL/6 (B6) was used as a surgical model. Expression of beta7 integrins was measured on recipient lymphocytes (CD4 and CD8 ) in spleen, blood, and mesenteric lymph nodes (MLN) using flow cytometry. To analyze the effects of blocking beta7 integrins on graft survival, either beta7-deficient B6 or wild-type B6 mice that were treated with mAb against beta7 were studied. RESULTS: After allogeneic SBT, there were markedly increased levels of alpha4beta7 recipient CD8 lymphocytes in MLN, blood, and spleen as early as 3 days postoperatively. In contrast, alpha4beta7 integrin levels in isograft recipients were similar to those of normal mice. Mean survival time of intestinal allografts was not affected by beta7 deficiency (7.3+/-1 days) compared with wild-type mice (7.5+/-0.8 days). However, mAb against beta7 integrins significantly prolonged graft survival (12.8+/-1 days) compared with treatment with control mAb (7.3+/-1 days, <0.001). Histologic changes of SBT rejection were significantly attenuated when mice were given mAb against beta7. CONCLUSION: As indicated by the increased levels of alpha4beta7 CD8 lymphocytes, activation of this integrin contributes to the immune response in SBT rejection. Furthermore, blocking beta7 integrins with mAb provides a suitable target for immunosuppressive therapy. The discrepancy in survival data obtained by mAb and beta7 deficiency may be a result of the more rapid activation of compensatory mechanisms in the knockout mice.

Animals↗

PubMed2002

Integrin alpha 2-deficient mice develop normally, are fertile, but display partially defective platelet interaction with collagen.

The integrin alpha(2)-subunit was ablated in mice by targeted deletion of the ITGA2 gene. alpha(2)-Deficient animals develop normally, are fertile, and reproduce. Surprisingly, no obvious anatomical or histological differences were observed in mutant mice. Besides its significance in tissue morphogenesis, integrin alpha(2)beta(1) has been reported to play a major role in hemostasis by mediating platelet adhesion and activation on subendothelial collagen. To define its role in hemostasis, alpha(2)-deficient platelets were analyzed for their capacity to adhere to and aggregate in response to fibrillar or soluble collagen type I. We show that aggregation of alpha(2)-deficient platelets to fibrillar collagen is delayed but not reduced, whereas aggregation to enzymatically digested soluble collagen is abolished. Furthermore, alpha(2)-deficient platelets normally adhere to fibrillar collagen. However, in the presence of an antibody against GPVI (activating platelet collagen receptor), adhesion of alpha(2)-deficient but not wild type platelets is abrogated. These results demonstrate that integrin alpha(2)beta(1) significantly contributes to platelet adhesion to (fibrillar) collagen, which is further confirmed by the abolished adhesion of alpha(2)-deficient platelets to soluble collagen. Thus, alpha(2)beta(1) plays a supportive rather than an essential role in platelet-collagen interactions. These results are in agreement with the observation that alpha(2)beta(1)-deficient animals suffer no bleeding anomalies.

Animals↗

PubMed2002

Microparticles derived from marine sponge collagen (SCMPs): preparation, characterization and suitability for dermal delivery of all-trans retinol.

Collagen microparticles were prepared using marine sponge collagen. For this purpose a previous method by Rössler et al. (J. Microencapsul. 12 (1995) 49) of emulsification and cross-linking of native calf collagen was modified. The modified method for sponge collagen microparticles (SCMPs) achieved a yield of 10%. Scanning electromicroscopic photographs showed spherical particles with a diameter of 120-300 nm and photon correlation spectroscopic measurements indicated particle size range from 126 (+/-2.9) to 2179 (+/-342) nm. This broad size distribution was caused by some agglomerates that could not be destroyed by ultrasonication. The surface charge was measured as a function of pH. At pH 2.8 the particles were nearly uncharged, at pH 9.0 the particles showed a strong negative charge of about -60 mV. The preformed SCMPs were loaded by adsorption of all-trans retinol. A loading of up to 8% was obtained. Retinol-loaded SCMPs were incorporated into hydrogels and drug stability was investigated. The in vitro penetration of retinol into hairless mice skin in this formulation was compared to retinol formulations without microparticles. The SCMPs had no influence on the chemical stability of retinol in the hydrogel. The dermal penetration of retinol into the skin increased significantly by approximately two-fold.

Administration, Cutaneous↗